1. Field of the Invention
The present invention relates to a phosphorus-containing epoxy resin, contained in various materials such as casting compounds, adhesives, and electrical insulating paint, having high flame retardancy; a phosphorus-containing epoxy resin composition, containing the resin, having high flame retardancy; a process for producing the resin; a sealant, used for manufacturing electrical components, containing the composition; a molding material containing the composition; and a laminate, such as a copper clad laminate included in printed wiring boards or electric circuit boards, containing the composition.
2. Description of the Related Art
Epoxy resins are used in various applications such as electronic components, electrical devices, automotive components, FRPs, and sporting goods because of the superior adhesion, heat resistance, and moldability. Copper clad laminates and sealants for such electronic components and electrical devices contain a flame retardant such as a halide or an antimony compound. However, the halide and antimony compound are harmful to human bodies. Therefore, an environmentally friendly flame retardant has been demanded.
Up to now, in order to render epoxy resins flame-retardant, the following techniques have been proposed: a technique in which an epoxy resin is blended with an additive flame retardant, a technique in which an epoxy resin is reformed by chemically bonding a reactive flame retardant to the epoxy resin, and the like.
Examples of the technique using the additive flame retardant include, for example, a technique, disclosed in Japanese Unexamined Patent Application Publication No. 5-25369, using hydrated alumina; a technique, disclosed in Japanese Unexamined Patent Application Publication No. 58-198521, using surface-treated red phosphorus, hydrated alumina, and/or silica powder; and a technique, disclosed in Japanese Unexamined Patent Application Publication No. 63-156860, using modified red phosphorus.
When molding materials contain the additive flame retardant, the moldability thereof is inferior because a large amount the flame retardant must be contained.
On the other hand, in the case of the reactive flame retardant, the content of the flame retardant may be low. Therefore, various techniques using the reactive flame retardant have been proposed.
Examples of such techniques include a technique, disclosed in Japanese Unexamined Patent Application Publication No. 57-195141, using tris(hydroxypropyl)-phosphine oxide; a technique, disclosed in Japanese Unexamined Patent Application Publication No. 63-95223, using a phosphine oxide derivative; a technique, disclosed in Japanese Unexamined Patent Application Publication Nos. 11-279258 and 11-166035, using an organic phosphorus compound; and a technique, disclosed in Japanese Unexamined Patent Application Publication Nos. 51-143620, 3-84025, 2-272014, and 2-269730, using epoxy phosphate prepared by allowing phosphonic acid to react with epichlorohydrin or a polyepoxy compound having an epoxy group. The phosphine oxide derivative is represented by the following formula (3):
wherein R5 represents a methylene or ethylene group, x represents an integer of 0 to 2, y represents an integer of 1 to 3, and x+y=3. The organic phosphorus compound is represented by the following formula:
wherein R represents an alkyl group with one to six carbon atoms and n represents an integer of 0 to 4.
A technique using a phosphorus-containing compound, which functions as a reactive flame retardant, is disclosed in Japanese Unexamined Patent Application Publication No. 2000-80251. This compound is represented by the following formula (6):
wherein R′ represents a group with two or more phenolic hydroxyl groups; n′ represents an integer of 0 to 3; R″ represents a linear or branched alkyl group, cyclohexyl group, cyclopentyl group, or aryl group with one to eight carbon atoms or a alkyl- or alkoxy-substituted alkyl or aryl group with one to 18 carbon atoms and may have a ring containing a P atom; and m is 0 or 1. Various phosphorus-containing compounds functioning as a reactive flame retardant are disclosed in this publication; however, a compound with the phosphorus-oxygen (P—O) bond only has flame retardancy in actual.
As described above, the various techniques for rendering the epoxy resin flame-retardant have been proposed. However, in the techniques using the reactive flame retardant, there are the following problems: the phosphorus content per unit weight in the epoxy resin cannot be sufficiently increased to exert the flame retardancy, and the flame retardancy cannot be enhanced even if a sufficient amount of phosphorus is added to the epoxy resin.
Most of known organic phosphorus compounds contained in the flame retardants for the epoxy resin have the P—O bond. Therefore, there is a problem in that such compounds are hydrolyzed. In particular, there is a problem in that electrical properties of electrical parts are deteriorated due to eluted phosphoric acid produced by the decomposition of an organic phosphorus compound when the electrical parts contain the epoxy resin, functioning as a flame retardant, having the P—O bond.